The last thing you want when playing a game on your Nintendo Wii console is screen interference. Many Wii games require precision control of the on screen action that can be made difficult is your picture isn't perfect. If you have a good quality TV or monitor there's no reason that you should have to suffer poor picture quality from your console.
Make sure that your Wii console is properly connected. Connect the AV multi out lead that came with your Wii to the back of the console and make sure the RCA in plugs are correctly connected to in ports on the back of your TV, monitor or other device. Make sure that the colour-coded RCA plugs correspond to their respective in ports.
Turn the console on and use the input select button on your TV, monitor other device to locate the Wii's signal.
Insert a disc and start a game.
Move all other electrical equipment away from the screen if you can still see the wavy lines. Cell phones, computers and even speakers can all interfere with some TVs, monitors or other devices, causing the picture to distort.
Start another game to see if there is a problem with disc if the problem persists.
Restart the console if the wavy lines are still visible.
Press the "Wii" button, "A" and then select the "Wii settings" icon.
Select "Screen" from the "Wii systems settings 1" menu. From here you can alter the screen position, widescreen settings and TV resolution so as your console is fully synchronised with your TV, monitor or other device.
Move your Wii and the TV, monitor or other device you're using to another room if changing the screen settings hasn't resolved the issue. If you are near to a major power source, its magnetic field could cause screen interference.
Connect your Wii console to another screen. If you still see wavy lines on the screen it's likely that your console is faulty. Contact the retailer that sold it to you or Nintendo arrange repair or replacement.